All of Peter Cushing's scenes in the film were shot in England, as Cushing disliked travelling abroad by this stage of his career. Ray Milland was only too happy to oblige the director and come to the UK for filming, as he used the opportunity to visit old friends and relatives back in his native South Wales.
The little girl who plays Lucy in the "Quebec Province 1975" segment of the film is Katrina Holden Bronson, the adopted daughter of Jill Ireland and Charles Bronson.
Susan Penhaligon received a bouquet of flowers from Peter Cushing on the first day she arrived on set to be in this film.
When Wilbur Gray (Peter Cushing) relates the incident concerning the fictional Hollywood actor Valentine De'ath (Donald Pleasence), for the "Hollywood 1936" segment of the film, he shows the evidence to Frank Richards (Ray Milland), which includes a still photo of Pleasence as the villain Ernst Stavro Blofeld with a white Persian cat on his lap from the James Bond film "You Only Live Twice" (1967).
The film's cinematographer, Harry Waxman, threatened to quit when he found that the production was mistreating the cats.